[PATCH v6 02/17] landlock: refactors landlock_find/insert_rule
Konstantin Meskhidze (A)
konstantin.meskhidze at huawei.com
Fri Jul 8 12:53:10 UTC 2022
7/7/2022 7:44 PM, Mickaël Salaün пишет:
>
> On 21/06/2022 10:22, Konstantin Meskhidze wrote:
>> Adds a new object union to support a socket port
>> rule type. Refactors landlock_insert_rule() and
>> landlock_find_rule() to support coming network
>> modifications. Now adding or searching a rule
>> in a ruleset depends on a rule_type argument
>> provided in refactored functions mentioned above.
>>
>> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze at huawei.com>
>> ---
>>
>> Changes since v5:
>> * Formats code with clang-format-14.
>>
>> Changes since v4:
>> * Refactors insert_rule() and create_rule() functions by deleting
>> rule_type from their arguments list, it helps to reduce useless code.
>>
>> Changes since v3:
>> * Splits commit.
>> * Refactors landlock_insert_rule and landlock_find_rule functions.
>> * Rename new_ruleset->root_inode.
>>
>> ---
>> security/landlock/fs.c | 7 ++-
>> security/landlock/ruleset.c | 105 ++++++++++++++++++++++++++----------
>> security/landlock/ruleset.h | 27 +++++-----
>> 3 files changed, 96 insertions(+), 43 deletions(-)
>>
>> diff --git a/security/landlock/fs.c b/security/landlock/fs.c
>> index e6da08ed99d1..46aedc2a05a8 100644
>> --- a/security/landlock/fs.c
>> +++ b/security/landlock/fs.c
>> @@ -173,7 +173,8 @@ int landlock_append_fs_rule(struct landlock_ruleset *const ruleset,
>> if (IS_ERR(object))
>> return PTR_ERR(object);
>> mutex_lock(&ruleset->lock);
>> - err = landlock_insert_rule(ruleset, object, access_rights);
>> + err = landlock_insert_rule(ruleset, object, 0, access_rights,
>> + LANDLOCK_RULE_PATH_BENEATH);
>> mutex_unlock(&ruleset->lock);
>> /*
>> * No need to check for an error because landlock_insert_rule()
>> @@ -204,7 +205,9 @@ find_rule(const struct landlock_ruleset *const domain,
>> inode = d_backing_inode(dentry);
>> rcu_read_lock();
>> rule = landlock_find_rule(
>> - domain, rcu_dereference(landlock_inode(inode)->object));
>> + domain,
>> + (uintptr_t)rcu_dereference(landlock_inode(inode)->object),
>> + LANDLOCK_RULE_PATH_BENEATH);
>> rcu_read_unlock();
>> return rule;
>> }
>> diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
>> index a3fd58d01f09..5f13f8a12aee 100644
>> --- a/security/landlock/ruleset.c
>> +++ b/security/landlock/ruleset.c
>> @@ -35,7 +35,7 @@ static struct landlock_ruleset *create_ruleset(const u32 num_layers)
>> return ERR_PTR(-ENOMEM);
>> refcount_set(&new_ruleset->usage, 1);
>> mutex_init(&new_ruleset->lock);
>> - new_ruleset->root = RB_ROOT;
>> + new_ruleset->root_inode = RB_ROOT;
>> new_ruleset->num_layers = num_layers;
>> /*
>> * hierarchy = NULL
>> @@ -69,7 +69,8 @@ static void build_check_rule(void)
>> }
>>
>> static struct landlock_rule *
>> -create_rule(struct landlock_object *const object,
>> +create_rule(struct landlock_object *const object_ptr,
>> + const uintptr_t object_data,
>> const struct landlock_layer (*const layers)[], const u32 num_layers,
>> const struct landlock_layer *const new_layer)
>> {
>> @@ -90,8 +91,15 @@ create_rule(struct landlock_object *const object,
>> if (!new_rule)
>> return ERR_PTR(-ENOMEM);
>> RB_CLEAR_NODE(&new_rule->node);
>> - landlock_get_object(object);
>> - new_rule->object = object;
>> +
>> + if (object_ptr) {
>> + landlock_get_object(object_ptr);
>> + new_rule->object.ptr = object_ptr;
>> + } else if (object_ptr && object_data) {
>
> Something is wrong with this second check: else + object_ptr?
It was your suggestion to use it like this:
" ....You can also add a WARN_ON_ONCE(object_ptr && object_data)."
Please check it here:
https://lore.kernel.org/linux-security-module/bc44f11f-0eaa-a5f6-c5dc-1d36570f1be1@digikod.net/
>
>
>> + WARN_ON_ONCE(1);
>> + return ERR_PTR(-EINVAL);
>> + }
>> +
>> new_rule->num_layers = new_num_layers;
>> /* Copies the original layer stack. */
>> memcpy(new_rule->layers, layers,
>> @@ -107,7 +115,7 @@ static void free_rule(struct landlock_rule *const rule)
>> might_sleep();
>> if (!rule)
>> return;
>> - landlock_put_object(rule->object);
>> + landlock_put_object(rule->object.ptr);
>> kfree(rule);
>> }
>>
>> @@ -143,26 +151,42 @@ static void build_check_ruleset(void)
>> * access rights.
>> */
>> static int insert_rule(struct landlock_ruleset *const ruleset,
>> - struct landlock_object *const object,
>> + struct landlock_object *const object_ptr,
>> + uintptr_t object_data, u16 rule_type,
>
> Use landlock_rule_type instead of u16, everywhere. It was part of my
> review/patch two versions ago (with other things), please take them into
> account:
> https://lore.kernel.org/r/92d498f0-c598-7413-6b7c-d19c5aec6cab@digikod.net
>
Ok. Thanks for the reminder.
>
>> const struct landlock_layer (*const layers)[],
>> size_t num_layers)
>> {
>> struct rb_node **walker_node;
>> struct rb_node *parent_node = NULL;
>> struct landlock_rule *new_rule;
>> + struct rb_root *root;
>>
>> might_sleep();
>> lockdep_assert_held(&ruleset->lock);
>> - if (WARN_ON_ONCE(!object || !layers))
>> + if (WARN_ON_ONCE(!layers))
>> return -ENOENT;
>> - walker_node = &(ruleset->root.rb_node);
>> + if (WARN_ON_ONCE(object_ptr && object_data))
>> + return -EINVAL;
>> + /* Chooses rb_tree structure depending on a rule type. */
>> + switch (rule_type) {
>> + case LANDLOCK_RULE_PATH_BENEATH:
>> + if (WARN_ON_ONCE(!object_ptr))
>> + return -ENOENT;
>> + object_data = (uintptr_t)object_ptr;
>> + root = &ruleset->root_inode;
>> + break;
>> + default:
>> + WARN_ON_ONCE(1);
>> + return -EINVAL;
>> + }
>> + walker_node = &root->rb_node;
>> while (*walker_node) {
>> struct landlock_rule *const this =
>> rb_entry(*walker_node, struct landlock_rule, node);
>>
>> - if (this->object != object) {
>> + if (this->object.data != object_data) {
>> parent_node = *walker_node;
>> - if (this->object < object)
>> + if (this->object.data < object_data)
>> walker_node = &((*walker_node)->rb_right);
>> else
>> walker_node = &((*walker_node)->rb_left);
>> @@ -194,11 +218,16 @@ static int insert_rule(struct landlock_ruleset *const ruleset,
>> * Intersects access rights when it is a merge between a
>> * ruleset and a domain.
>> */
>> - new_rule = create_rule(object, &this->layers, this->num_layers,
>> - &(*layers)[0]);
>> + switch (rule_type) {
>> + case LANDLOCK_RULE_PATH_BENEATH:
>> + new_rule = create_rule(object_ptr, 0, &this->layers,
>> + this->num_layers, &(*layers)[0]);
>> + break;
>> + }
>> if (IS_ERR(new_rule))
>> return PTR_ERR(new_rule);
>> - rb_replace_node(&this->node, &new_rule->node, &ruleset->root);
>> + rb_replace_node(&this->node, &new_rule->node,
>> + &ruleset->root_inode);
>> free_rule(this);
>> return 0;
>> }
>> @@ -207,11 +236,15 @@ static int insert_rule(struct landlock_ruleset *const ruleset,
>> build_check_ruleset();
>> if (ruleset->num_rules >= LANDLOCK_MAX_NUM_RULES)
>> return -E2BIG;
>> - new_rule = create_rule(object, layers, num_layers, NULL);
>> + switch (rule_type) {
>> + case LANDLOCK_RULE_PATH_BENEATH:
>> + new_rule = create_rule(object_ptr, 0, layers, num_layers, NULL);
>> + break;
>> + }
>> if (IS_ERR(new_rule))
>> return PTR_ERR(new_rule);
>> rb_link_node(&new_rule->node, parent_node, walker_node);
>> - rb_insert_color(&new_rule->node, &ruleset->root);
>> + rb_insert_color(&new_rule->node, &ruleset->root_inode);
>> ruleset->num_rules++;
>> return 0;
>> }
>> @@ -229,8 +262,9 @@ static void build_check_layer(void)
>>
>> /* @ruleset must be locked by the caller. */
>> int landlock_insert_rule(struct landlock_ruleset *const ruleset,
>> - struct landlock_object *const object,
>> - const access_mask_t access)
>> + struct landlock_object *const object_ptr,
>> + const uintptr_t object_data,
>> + const access_mask_t access, const u16 rule_type)
>> {
>> struct landlock_layer layers[] = { {
>> .access = access,
>> @@ -239,7 +273,8 @@ int landlock_insert_rule(struct landlock_ruleset *const ruleset,
>> } };
>>
>> build_check_layer();
>> - return insert_rule(ruleset, object, &layers, ARRAY_SIZE(layers));
>> + return insert_rule(ruleset, object_ptr, object_data, rule_type, &layers,
>> + ARRAY_SIZE(layers));
>> }
>>
>> static inline void get_hierarchy(struct landlock_hierarchy *const hierarchy)
>> @@ -284,8 +319,8 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
>> dst->access_masks[dst->num_layers - 1] = src->access_masks[0];
>>
>> /* Merges the @src tree. */
>> - rbtree_postorder_for_each_entry_safe(walker_rule, next_rule, &src->root,
>> - node) {
>> + rbtree_postorder_for_each_entry_safe(walker_rule, next_rule,
>> + &src->root_inode, node) {
>> struct landlock_layer layers[] = { {
>> .level = dst->num_layers,
>> } };
>> @@ -299,7 +334,8 @@ static int merge_ruleset(struct landlock_ruleset *const dst,
>> goto out_unlock;
>> }
>> layers[0].access = walker_rule->layers[0].access;
>> - err = insert_rule(dst, walker_rule->object, &layers,
>> + err = insert_rule(dst, walker_rule->object.ptr, 0,
>> + LANDLOCK_RULE_PATH_BENEATH, &layers,
>> ARRAY_SIZE(layers));
>> if (err)
>> goto out_unlock;
>> @@ -327,8 +363,9 @@ static int inherit_ruleset(struct landlock_ruleset *const parent,
>>
>> /* Copies the @parent tree. */
>> rbtree_postorder_for_each_entry_safe(walker_rule, next_rule,
>> - &parent->root, node) {
>> - err = insert_rule(child, walker_rule->object,
>> + &parent->root_inode, node) {
>> + err = insert_rule(child, walker_rule->object.ptr, 0,
>> + LANDLOCK_RULE_PATH_BENEATH,
>> &walker_rule->layers,
>> walker_rule->num_layers);
>> if (err)
>> @@ -361,7 +398,8 @@ static void free_ruleset(struct landlock_ruleset *const ruleset)
>> struct landlock_rule *freeme, *next;
>>
>> might_sleep();
>> - rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root, node)
>> + rbtree_postorder_for_each_entry_safe(freeme, next, &ruleset->root_inode,
>> + node)
>> free_rule(freeme);
>> put_hierarchy(ruleset->hierarchy);
>> kfree(ruleset);
>> @@ -453,20 +491,29 @@ landlock_merge_ruleset(struct landlock_ruleset *const parent,
>> */
>> const struct landlock_rule *
>> landlock_find_rule(const struct landlock_ruleset *const ruleset,
>> - const struct landlock_object *const object)
>> + const uintptr_t object_data, const u16 rule_type)
>> {
>> const struct rb_node *node;
>>
>> - if (!object)
>> + if (!object_data)
>> return NULL;
>> - node = ruleset->root.rb_node;
>> +
>> + switch (rule_type) {
>> + case LANDLOCK_RULE_PATH_BENEATH:
>> + node = ruleset->root_inode.rb_node;
>> + break;
>> + default:
>> + WARN_ON_ONCE(1);
>> + return NULL;
>> + }
>> +
>> while (node) {
>> struct landlock_rule *this =
>> rb_entry(node, struct landlock_rule, node);
>>
>> - if (this->object == object)
>> + if (this->object.data == object_data)
>> return this;
>> - if (this->object < object)
>> + if (this->object.data < object_data)
>> node = node->rb_right;
>> else
>> node = node->rb_left;
>> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
>> index bd7ab39859bf..a22d132c32a7 100644
>> --- a/security/landlock/ruleset.h
>> +++ b/security/landlock/ruleset.h
>> @@ -53,15 +53,17 @@ struct landlock_rule {
>> */
>> struct rb_node node;
>> /**
>> - * @object: Pointer to identify a kernel object (e.g. an inode). This
>> - * is used as a key for this ruleset element. This pointer is set once
>> - * and never modified. It always points to an allocated object because
>> - * each rule increments the refcount of its object.
>> - */
>> - struct landlock_object *object;
>> - /**
>> - * @num_layers: Number of entries in @layers.
>> + * @object: A union to identify either a kernel object (e.g. an inode) or
>> + * a raw data value (e.g. a network socket port). This is used as a key
>> + * for this ruleset element. This pointer/@object.ptr/ is set once and
>> + * never modified. It always points to an allocated object because each
>> + * rule increments the refcount of its object (for inodes).;
>> */
>> + union {
>> + struct landlock_object *ptr;
>> + uintptr_t data;
>> + } object;
>> +
>> u32 num_layers;
>> /**
>> * @layers: Stack of layers, from the latest to the newest, implemented
>> @@ -98,7 +100,7 @@ struct landlock_ruleset {
>> * nodes. Once a ruleset is tied to a process (i.e. as a domain), this
>> * tree is immutable until @usage reaches zero.
>> */
>> - struct rb_root root;
>> + struct rb_root root_inode;
>> /**
>> * @hierarchy: Enables hierarchy identification even when a parent
>> * domain vanishes. This is needed for the ptrace protection.
>> @@ -160,8 +162,9 @@ void landlock_put_ruleset(struct landlock_ruleset *const ruleset);
>> void landlock_put_ruleset_deferred(struct landlock_ruleset *const ruleset);
>>
>> int landlock_insert_rule(struct landlock_ruleset *const ruleset,
>> - struct landlock_object *const object,
>> - const access_mask_t access);
>> + struct landlock_object *const object_ptr,
>> + const uintptr_t object_data,
>> + const access_mask_t access, const u16 rule_type);
>>
>> struct landlock_ruleset *
>> landlock_merge_ruleset(struct landlock_ruleset *const parent,
>> @@ -169,7 +172,7 @@ landlock_merge_ruleset(struct landlock_ruleset *const parent,
>>
>> const struct landlock_rule *
>> landlock_find_rule(const struct landlock_ruleset *const ruleset,
>> - const struct landlock_object *const object);
>> + const uintptr_t object_data, const u16 rule_type);
>>
>> static inline void landlock_get_ruleset(struct landlock_ruleset *const ruleset)
>> {
>> --
>> 2.25.1
>>
> .
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